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  <section id="sequence-protocol">
<span id="sequence"></span><h1>Sequence Protocol<a class="headerlink" href="#sequence-protocol" title="Permalink to this headline">¶</a></h1>
<dl class="function">
<dt id="c.PySequence_Check">
int <code class="sig-name descname">PySequence_Check</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Check" title="Permalink to this definition">¶</a></dt>
<dd><p>Return <code class="docutils literal notranslate"><span class="pre">1</span></code> if the object provides sequence protocol, and <code class="docutils literal notranslate"><span class="pre">0</span></code> otherwise.
Note that it returns <code class="docutils literal notranslate"><span class="pre">1</span></code> for Python classes with a <a class="reference internal" href="../reference/datamodel.html#object.__getitem__" title="object.__getitem__"><code class="xref py py-meth docutils literal notranslate"><span class="pre">__getitem__()</span></code></a>
method unless they are <a class="reference internal" href="../library/stdtypes.html#dict" title="dict"><code class="xref py py-class docutils literal notranslate"><span class="pre">dict</span></code></a> subclasses since in general case it
is impossible to determine what the type of keys it supports.  This
function always succeeds.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Size">
Py_ssize_t <code class="sig-name descname">PySequence_Size</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Size" title="Permalink to this definition">¶</a></dt>
<dt id="c.PySequence_Length">
Py_ssize_t <code class="sig-name descname">PySequence_Length</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Length" title="Permalink to this definition">¶</a></dt>
<dd><p id="index-0">Returns the number of objects in sequence <em>o</em> on success, and <code class="docutils literal notranslate"><span class="pre">-1</span></code> on
failure.  This is equivalent to the Python expression <code class="docutils literal notranslate"><span class="pre">len(o)</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Concat">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_Concat</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o1</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o2</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Concat" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the concatenation of <em>o1</em> and <em>o2</em> on success, and <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure.
This is the equivalent of the Python expression <code class="docutils literal notranslate"><span class="pre">o1</span> <span class="pre">+</span> <span class="pre">o2</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Repeat">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_Repeat</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> count</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Repeat" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the result of repeating sequence object <em>o</em> <em>count</em> times, or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on
failure.  This is the equivalent of the Python expression <code class="docutils literal notranslate"><span class="pre">o</span> <span class="pre">*</span> <span class="pre">count</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_InPlaceConcat">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_InPlaceConcat</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o1</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o2</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_InPlaceConcat" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the concatenation of <em>o1</em> and <em>o2</em> on success, and <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure.
The operation is done <em>in-place</em> when <em>o1</em> supports it.  This is the equivalent
of the Python expression <code class="docutils literal notranslate"><span class="pre">o1</span> <span class="pre">+=</span> <span class="pre">o2</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_InPlaceRepeat">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_InPlaceRepeat</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> count</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_InPlaceRepeat" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the result of repeating sequence object <em>o</em> <em>count</em> times, or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on
failure.  The operation is done <em>in-place</em> when <em>o</em> supports it.  This is the
equivalent of the Python expression <code class="docutils literal notranslate"><span class="pre">o</span> <span class="pre">*=</span> <span class="pre">count</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_GetItem">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_GetItem</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_GetItem" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the <em>i</em>th element of <em>o</em>, or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure. This is the equivalent of
the Python expression <code class="docutils literal notranslate"><span class="pre">o[i]</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_GetSlice">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_GetSlice</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i1</em>, Py_ssize_t<em> i2</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_GetSlice" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the slice of sequence object <em>o</em> between <em>i1</em> and <em>i2</em>, or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on
failure. This is the equivalent of the Python expression <code class="docutils literal notranslate"><span class="pre">o[i1:i2]</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_SetItem">
int <code class="sig-name descname">PySequence_SetItem</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *v</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_SetItem" title="Permalink to this definition">¶</a></dt>
<dd><p>Assign object <em>v</em> to the <em>i</em>th element of <em>o</em>.  Raise an exception
and return <code class="docutils literal notranslate"><span class="pre">-1</span></code> on failure; return <code class="docutils literal notranslate"><span class="pre">0</span></code> on success.  This
is the equivalent of the Python statement <code class="docutils literal notranslate"><span class="pre">o[i]</span> <span class="pre">=</span> <span class="pre">v</span></code>.  This function <em>does
not</em> steal a reference to <em>v</em>.</p>
<p>If <em>v</em> is <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, the element is deleted, however this feature is
deprecated in favour of using <a class="reference internal" href="#c.PySequence_DelItem" title="PySequence_DelItem"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_DelItem()</span></code></a>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_DelItem">
int <code class="sig-name descname">PySequence_DelItem</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_DelItem" title="Permalink to this definition">¶</a></dt>
<dd><p>Delete the <em>i</em>th element of object <em>o</em>.  Returns <code class="docutils literal notranslate"><span class="pre">-1</span></code> on failure.  This is the
equivalent of the Python statement <code class="docutils literal notranslate"><span class="pre">del</span> <span class="pre">o[i]</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_SetSlice">
int <code class="sig-name descname">PySequence_SetSlice</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i1</em>, Py_ssize_t<em> i2</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *v</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_SetSlice" title="Permalink to this definition">¶</a></dt>
<dd><p>Assign the sequence object <em>v</em> to the slice in sequence object <em>o</em> from <em>i1</em> to
<em>i2</em>.  This is the equivalent of the Python statement <code class="docutils literal notranslate"><span class="pre">o[i1:i2]</span> <span class="pre">=</span> <span class="pre">v</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_DelSlice">
int <code class="sig-name descname">PySequence_DelSlice</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i1</em>, Py_ssize_t<em> i2</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_DelSlice" title="Permalink to this definition">¶</a></dt>
<dd><p>Delete the slice in sequence object <em>o</em> from <em>i1</em> to <em>i2</em>.  Returns <code class="docutils literal notranslate"><span class="pre">-1</span></code> on
failure.  This is the equivalent of the Python statement <code class="docutils literal notranslate"><span class="pre">del</span> <span class="pre">o[i1:i2]</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Count">
Py_ssize_t <code class="sig-name descname">PySequence_Count</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *value</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Count" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the number of occurrences of <em>value</em> in <em>o</em>, that is, return the number
of keys for which <code class="docutils literal notranslate"><span class="pre">o[key]</span> <span class="pre">==</span> <span class="pre">value</span></code>.  On failure, return <code class="docutils literal notranslate"><span class="pre">-1</span></code>.  This is
equivalent to the Python expression <code class="docutils literal notranslate"><span class="pre">o.count(value)</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Contains">
int <code class="sig-name descname">PySequence_Contains</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *value</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Contains" title="Permalink to this definition">¶</a></dt>
<dd><p>Determine if <em>o</em> contains <em>value</em>.  If an item in <em>o</em> is equal to <em>value</em>,
return <code class="docutils literal notranslate"><span class="pre">1</span></code>, otherwise return <code class="docutils literal notranslate"><span class="pre">0</span></code>. On error, return <code class="docutils literal notranslate"><span class="pre">-1</span></code>.  This is
equivalent to the Python expression <code class="docutils literal notranslate"><span class="pre">value</span> <span class="pre">in</span> <span class="pre">o</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Index">
Py_ssize_t <code class="sig-name descname">PySequence_Index</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, <a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *value</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Index" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the first index <em>i</em> for which <code class="docutils literal notranslate"><span class="pre">o[i]</span> <span class="pre">==</span> <span class="pre">value</span></code>.  On error, return
<code class="docutils literal notranslate"><span class="pre">-1</span></code>.    This is equivalent to the Python expression <code class="docutils literal notranslate"><span class="pre">o.index(value)</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_List">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_List</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_List" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return a list object with the same contents as the sequence or iterable <em>o</em>,
or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure.  The returned list is guaranteed to be new.  This is
equivalent to the Python expression <code class="docutils literal notranslate"><span class="pre">list(o)</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Tuple">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_Tuple</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Tuple" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p id="index-1">Return a tuple object with the same contents as the sequence or iterable <em>o</em>,
or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure.  If <em>o</em> is a tuple, a new reference will be returned,
otherwise a tuple will be constructed with the appropriate contents.  This is
equivalent to the Python expression <code class="docutils literal notranslate"><span class="pre">tuple(o)</span></code>.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Fast">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_Fast</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, const char<em> *m</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Fast" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the sequence or iterable <em>o</em> as an object usable by the other
<code class="docutils literal notranslate"><span class="pre">PySequence_Fast*</span></code> family of functions. If the object is not a sequence or
iterable, raises <a class="reference internal" href="../library/exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a> with <em>m</em> as the message text. Returns
<code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">PySequence_Fast*</span></code> functions are thus named because they assume
<em>o</em> is a <a class="reference internal" href="tuple.html#c.PyTupleObject" title="PyTupleObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyTupleObject</span></code></a> or a <a class="reference internal" href="list.html#c.PyListObject" title="PyListObject"><code class="xref c c-type docutils literal notranslate"><span class="pre">PyListObject</span></code></a> and access
the data fields of <em>o</em> directly.</p>
<p>As a CPython implementation detail, if <em>o</em> is already a sequence or list, it
will be returned.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Fast_GET_SIZE">
Py_ssize_t <code class="sig-name descname">PySequence_Fast_GET_SIZE</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Fast_GET_SIZE" title="Permalink to this definition">¶</a></dt>
<dd><p>Returns the length of <em>o</em>, assuming that <em>o</em> was returned by
<a class="reference internal" href="#c.PySequence_Fast" title="PySequence_Fast"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_Fast()</span></code></a> and that <em>o</em> is not <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.  The size can also be
gotten by calling <a class="reference internal" href="#c.PySequence_Size" title="PySequence_Size"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_Size()</span></code></a> on <em>o</em>, but
<a class="reference internal" href="#c.PySequence_Fast_GET_SIZE" title="PySequence_Fast_GET_SIZE"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_Fast_GET_SIZE()</span></code></a> is faster because it can assume <em>o</em> is a
list or tuple.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Fast_GET_ITEM">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_Fast_GET_ITEM</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Fast_GET_ITEM" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: Borrowed reference.</em><p>Return the <em>i</em>th element of <em>o</em>, assuming that <em>o</em> was returned by
<a class="reference internal" href="#c.PySequence_Fast" title="PySequence_Fast"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_Fast()</span></code></a>, <em>o</em> is not <code class="docutils literal notranslate"><span class="pre">NULL</span></code>, and that <em>i</em> is within bounds.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_Fast_ITEMS">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>** <code class="sig-name descname">PySequence_Fast_ITEMS</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_Fast_ITEMS" title="Permalink to this definition">¶</a></dt>
<dd><p>Return the underlying array of PyObject pointers.  Assumes that <em>o</em> was returned
by <a class="reference internal" href="#c.PySequence_Fast" title="PySequence_Fast"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_Fast()</span></code></a> and <em>o</em> is not <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
<p>Note, if a list gets resized, the reallocation may relocate the items array.
So, only use the underlying array pointer in contexts where the sequence
cannot change.</p>
</dd></dl>

<dl class="function">
<dt id="c.PySequence_ITEM">
<a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a>* <code class="sig-name descname">PySequence_ITEM</code><span class="sig-paren">(</span><a class="reference internal" href="structures.html#c.PyObject" title="PyObject">PyObject</a><em> *o</em>, Py_ssize_t<em> i</em><span class="sig-paren">)</span><a class="headerlink" href="#c.PySequence_ITEM" title="Permalink to this definition">¶</a></dt>
<dd><em class="refcount">Return value: New reference.</em><p>Return the <em>i</em>th element of <em>o</em> or <code class="docutils literal notranslate"><span class="pre">NULL</span></code> on failure. Faster form of
<a class="reference internal" href="#c.PySequence_GetItem" title="PySequence_GetItem"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_GetItem()</span></code></a> but without checking that
<a class="reference internal" href="#c.PySequence_Check" title="PySequence_Check"><code class="xref c c-func docutils literal notranslate"><span class="pre">PySequence_Check()</span></code></a> on <em>o</em> is true and without adjustment for negative
indices.</p>
</dd></dl>

</section>


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